Vortec 5300 5.3L V8
I have a misfire on cylinders 1, 5, 6, and 8 - throwing a P0300 code. Engine seems to run normally, not rough, and does not lack power. I have replaced fuel pump, MAF, intake gaskets, spark plus, wires, coils.
I am not sure where else to look. Cam/Crank position sensor? Bad Cat? Vacuum leak...